Frequency Stabilization of Pulsed Injection-Seeded OPO Based on Optical Heterodyne Technique**Supported by the National Key Research and Development Program of China under Grant No 2016YFC1400902, the National Natural Science Foundation of China under Grant Nos 61505230 and 61475170, and the Shanghai Natural Science Foundation under Grant No 15ZR1445000.

Abstract

A frequency stabilizing system for a pulsed injection seeded 1550nm optical parametric oscillator (OPO) at 20 Hz repetition rate is demonstrated. The optical heterodyne method is used to measure the frequency difference between the seed laser and the OPO output. Using the frequency difference as the error signal, a proportionalintegral controller in combination with a scanner is applied to stably match the OPO cavity length to the seed laser frequency. The root-mean-square (rms) error of the frequency discrimination method is <0.07MHz according to a ‘frequency shifting-chopping-beat’ evaluation. The frequency fluctuation of the frequency-stabilized OPO is 0.29MHz (rms), and the Allan deviation is less than 20 kHz for averaging time of more than 3 s.